Symptoms of abnormal heart rhythm are generally referred to as cardiac arrhythmias, with an abnormally slow rhythm being classified as a bradycardia and an abnormally rapid rhythm being referred to as a tachycardia. The present invention is concerned with the treatment of tachycardias which are frequently caused by the presence of an "arrhythmogenic site" or "accessory atrioventricular pathway" close to the inner surface of the chambers of the heart. The heart includes a number of normal pathways which are responsible for the propagation of signals necessary for normal electrical mechanical function. The presence of arrhythmogenic sites or accessory pathways can bypass or short circuit the normal pathways, potentially resulting in very rapid heart contractions, referred to here as tachycardias.
Treatment of tachycardias may be accomplished by a variety of approaches, including drugs, surgery, implantable pacemakers/defibrillators, and catheter ablation. While drugs may be the treatment of choice for many patients, they only mask the symptoms and do not cure the underlying cause. Implantable devices only correct the arrhythmia after it occurs. Surgical and catheter-based treatments, in contrast, will actually cure the problem, usually by ablating the abnormal arrhythmogenic tissue or accessory pathway responsible for the tachycardia. It is important for the physician to be able to accurately steer the catheter to the ablation site. Once at the site, it is important for the physician to control the emission of energy within the body used to ablate the tissue.
Of particular interest to the present invention are radiofrequency (RF) ablation protocols which have been proven to be highly effective in tachycardia treatment while exposing the patient to minimum side effects and risks. Radiofrequency catheter ablation is generally performed after an initial mapping procedure where the locations of the arrhythmogenic sites and accessory pathways are determined. After mapping, a catheter having a suitable large electrode is introduced to the appropriate heart chamber and manipulated so that the electrode lies right on the target tissue. RF energy is then applied through the electrode to the cardiac tissue in order to ablate a region of the tissue which forms part of arrhythmogenic site or the accessory pathway. By successfully destroying that tissue, the abnormal signal patterns responsible for the tachycardia cannot be sustained.
Catheters utilized in radiofrequency ablation are inserted into a major vein or artery, usually in the neck or groin area, and guided into the chambers of the heart by appropriate manipulation through the vein or artery. The tip portion of the catheter must be steerable by the user from the proximal end of the catheter, so that the electrodes at the distal portion can be positioned against the tissue region to be ablated. The catheter must have a great deal of flexibility in order to follow the pathway of the major blood vessels into the heart, and the catheter must permit user manipulation of the tip portion. In addition, the distal portion of the catheter must be sufficiently resilient in order to be positioned against the wall of the atrium or ventricle and maintained in a contact position during ablation without being displaced by the movement of the beating heart. Along with the steerability, flexibility and resiliency, the catheter must have a sufficient degree of torsional stiffness to permit user manipulation from the proximal end.
Steerable catheters are known for use in a variety of medical procedures. For example, see U.S. Pat. No. 5,318,525 to West, U.S. Pat. No. 5,318,041 to DuBois, U.S. Pat. No. 5,275,151 to Shockey, U.S. Pat. No. 4,998,916 to Hammerslag, U.S. Pat. No. 4,960,134 to Webster, Jr., U.S. Pat. No. 4,944,727 to McCoy, U.S. Pat. No. 4,838,859 to Strassmann, U.S. Pat. No. 4,826,087 to Chinery, U.S. Pat. No. 4,753,223 to Bremer, U.S. Pat. No. 4,685,457 to Donenfeld, U.S. Pat. No. 3,605,725 to Bentov, and U.S. Pat. No. 3,470,876 to Barchilon. Typically, such catheters employ a plurality of steering wires, usually three or more, extending from a steering mechanism at the proximal end of the catheter ("the handle") to an anchor point at the distal portion of the catheter. By tensioning certain of the steering wires from the controller at the handle, the tip portion of the catheter can be manipulated in a desired direction.
A handful of U.S. patents on endoscopes and other apparatus teach the art of disengaging the disposable portion of a device from its more-expensive fixture base, such as a handle station, an imaging station or video display. They include: U.S. Pat. No. 4,519,391 to Murakoshi, U.S. Pat. No. 4,534,339 to Collins et al., U.S. Pat. No. 4,911,148 to Sosnowski et al., U.S. Pat. No. 5,571,100 to Goble et al., U.S. Pat. No. 4,919,112 to Siegmund, U.S. Pat. No. 5,545,200 to West et al., U.S. Pat. No. 5,465,733 to Hinohara et al., U.S. Pat. No. 5,423,740 to Sullivan et al., U.S. Pat. No. 4,499,895 to Takayama and U.S. Pat. No. 5,487,757 to Truckai et al. None of the above-mentioned patents disclose the quick coupling and locking of a disposable catheter shaft to its handle involving the mechanical steering, electrical conducting, and energy delivery wires.
While electrophysiology mapping study and radiofrequency ablation procedure using existing steerable catheters have had promising results, due to potential cross-contamination concerns from a prior patient having AIDS, hepatitis, or unknown diseases, the existing catheter is considered a disposal device and is recommended for one-time use only. Even though certain hospital or clinician might tempt to re-sterilize and re-use the soiled catheter, the re-sterilization process might actually cause the catheter to deform or degrade, and render the catheter less effective and less safe for its intended use. In an electrophysiology procedure, only the catheter shaft portion which contacts human blood and tissue might be potentially contaminated.
In the present medical practices, the whole catheter system including the catheter shaft portion and the handle portion is being discarded. The need for recycle and reuse of the handle portion of a steerable catheter is obvious and makes good sense with respect to health aspects, environmental reasons, cost consideration, and advanced technology of this invention. In a representative steerable electrophysiology catheter, the cost of the handle portion is estimated to be more than four times of the cost of the disposable catheter shaft portion. Though in a previous patent, U.S. Pat. No. 4,911,148 to Sosnowski et al. teaches an endoscope with detachable flexible shaft assembly, it did not disclose a disposable catheter shaft having a mechanical, electrical, and energy delivery wires. The concept of a steerable catheter having a disposable catheter shaft for electrophysiology study and ablation procedure is novel in that the electricity and radiofrequency energy are transmitted through a quick coupling and locking connecting unit.
For these and other reasons, it would be desirable to provide a steerable catheter system suitable for mapping and radiofrequency ablation which has a quick exchangeable connection mechanism. Therefore, a new catheter tubing shaft can be quickly connected to the handle means for electrophysiology procedures.